The con came to an end Saturday night, after the student and a friend went out to dinner with O'Reilly.
His frequent presence in the dorm had attracted the attention of other Hollis residents, one of whom contacted the dorm's proctor, who then called the Harvard police.
HUPD officers were waiting at Hollis when the trio returned from dinner. At the time, O'Reilly was wearing a Harvard Business School T-shirt. According to McNamara, con artists who prey on students often wear school-related apparel.
"It seems to help students think that they belong," she said.
Police said they issued O'Reilly a verbal trespass warning. If he is found on campus again, he risks arrest.
The victim said she felt O'Reilly had taken advantage of her, but said that if the same progression of events occurred again, she would act the same way.
"The worst thing he did was mislead," the student said. She said she did notice that her student ID card was missing.
"We presume he won't come back," McNamara said. "But if he does, watch out and call us."